I never mounted an SSD internally. But I did try one in a USB 3 Docking station. The sequential read/write benchmarks were only 10 or 15% faster than WD Black Sata III 640 GB. But the random benchmarks were nearly as fast as the sequential. This made it killer for video muxing right in the dock. I had an MP4 converter that only processed the audio and remuxed to output .mp4 files.
The program was portable. I had the program folder, temp, source, and destination folders all on the SSD. Also the MP4 program was multi-threaded. If I loaded it up with a few files I could just watch the progressbar slide across. It was fun to do those jobs.